Hi CHB,
1,6FSI's don't use conventional spark plugs. You need coil packs, which are much more complex than spark plugs. In theory they should last longer too, but early components failed regularly. An updated version was introduced but I don't have the exact dates- but I do have the new versions and they are better. If your coil packs have failed the warranty period for these was extended to 5 years from first registration of the vehicle and you can have them replaced under guarantee at the dealers. If not I think they cost in the region of £72 each from Audi dealers, maybe less from VW/Skoda or SEAT.